1. Field of the Invention
This Application Claims the benefit of priority to Korean Patent Application 10-2012-0097037 filed on Sep. 3, 2012. The present invention relates generally to snap rings having 5 multiple rollers and, more particularly, to a snap ring having multiple rollers which is configured such that pressure which is applied from a purse line to the snap ring or the multiple rollers is distributed to two adjacent rollers rather than being focused on only one roller.
2. Description of the Related Art
Generally, purse seines are a kind of fishing net and are equipment used for fishing sardines, horse mackerels, mackerels, bonitos, tuna, etc. Such a purse seine and a conventional snap ring are illustrated in FIGS. 1 and 2.
As shown in FIGS. 1 and 2, a purse seine 200 has a rectangular shape, the central portion of which is slightly wider than other portions. Furthermore, a plurality of buoyancy units 202 are provided along the upper edge of the purse seine 200 in order to make it possible for the upper edge of the purse seine 200 to float on water, and bridle chains 205 are provided under the lower edge of the purse seine 200 so as to make it possible for the lower edge of the purse seine 200 to sink under the water surface. By virtue of the buoyancy units 202 and the bridle chains 205, the purse seine 200 can spread in the vertical direction in the water. Typically, the purse seine 200 is deployed in the water in an approximately circular shape so as to catch fish.
Furthermore, a purse line 210 which is used to haul in the purse seine 200 which has been deployed in a circular shape is disposed along the lower edge of the purse seine 200. The purse line 210 is coupled to the ends of the bridle chains 205 through connectors which are called snap rings 100. In detail, connection members 207 such as ropes or straps are connected to the ends of the bridle chains 205. Each connection member 207 is connected to a first end of the corresponding snap ring 100. The purse line 210 passes through second ends of the snap rings 140, thereby coupling the purse line 210 to the bridle chains 205. To haul in the purse seine 200, when the purse line 210 is pulled by a hydraulic purse winch provided on a fishing boat 220, the bridle chains 205 of the purse seine 200 are also pulled, and thus fish are confined while the purse seine 200 is hauled in.
However, in the case of the snap ring 100 according to the conventional technique, due to the weight of the fish and the purse seine 200 being hauled in, a relatively large frictional force is generated on the contact surface between the purse line 200 and the snap rings 100, thus inducing extreme abrasion of the surfaces of the purse line 210 and the snap rings 100, possibly resulting in tearing. This seriously interferes with the fishing operation. Furthermore, maintenance costs increase due to frequent replacement of the purse line 210 or the snap ring 100, thus resulting in reduced income.
Furthermore, because of the large load applied to each snap ring 100, the snap ring 100 may be broken. If the purse seine 200 is caught by the broken snap ring 100, the purse seine 200 may be entangled in the snap ring 100 or be torn by tidal currents or because of imbalance of the load, whereby a serious accident pertaining to the purse seine 200 may occur. As such, the operation of hauling in the purse seine 200 may not be smoothly carried out.
In an effort to overcome the above-mentioned problems, a snap ring having multiple rollers was proposed in Korean Patent Registration No. 10-0986008 (Date: Sep. 30, 2010) which was filed by the applicant of the present invention. The object of the snap ring having multiple rollers is to reduce frictional force generated on contact surfaces between a purse line and the snap ring.
FIG. 3 illustrates the conventional snap ring having multiple rollers. Referring to FIG. 3, the snap ring 100 for coupling a purse line to a purse seine includes: a frame 110 which has a first end connected to the purse seine and a second end through which the purse line passes; and a plurality of rollers which are rotatably provided in the frame 100 at positions at which the purse line is brought into contact with the frame 100. The multiple rollers include first and second side rollers 141 and 142 which are disposed in opposite side parts of the frame 100, and an intermediate roller 143 which is provided to span the opposite side parts of the frame 110 and is oriented such that opposite ends thereof respectively face the first and second side rollers 141 and 142.
When the purse line is placed through the frame 110, the purse line is positioned such that a first side thereof is brought into contact with either the first side roller 141 or the second side roller 142, and a second side thereof is brought into contact with the intermediate roller 143. In this state, when the purse line is moved, the load of the purse line is distributed to two rollers, for example, the first side roller 141 and the intermediate roller 143, which make contact with the purse line. Further, friction between the purse line and the frame 110 can be reduced by rotation of the first side roller 141 and the intermediate roller 143.
Meanwhile, a ship used for fishing operations generally pitches and rolls very easily in response to conditions of the sea. The purse line connected to the ship is also easily moved forwards, backwards, leftwards or rightwards. In the conventional snap ring 100 having multiple rollers, the first side roller 141 and the intermediate roller 143 or the second side roller 142 and the intermediate roller 143 form a right angle. Thus, when the purse line is disposed on only the first side roller 141 or the second side roller 142, the purse line cannot smoothly slide towards the intermediate roller 143, and the hauling operation is carried out with the purse line being disposed on only the first side roller 141 or the second side roller 142. In this case, the load of the purse line is concentrated on only one portion, that is, the first or second side roller 141 or 142 on which the purse line is disposed, rather than being distributed to two portions, that is, to the first side roller 141 and the intermediate roller 143 or to the second side roller 142 and the intermediate roller 143.
Eventually, excessive pressure is applied to the snap ring 100, thus reducing the lifetime of the snap ring 100, thereby resulting in an increase in the replacement costs of the snap ring 100.
Furthermore, the conventional snap ring 100 further includes a locking unit 150 which is provided in the frame 110 to open or close a frame opening which is formed in the frame 110 to allow the purse line to be connected to the snap ring 100. The locking unit 150 includes a first cylinder 151 which is hinged at a first end thereof to a part of the frame that corresponds to a first end of the frame opening. A second end of the first cylinder is disposed in the frame 110 at a position corresponding to a second end of the frame opening. The locking unit 150 further includes a second cylinder 160 which slides along the first cylinder 151 to open or close the frame opening.
Furthermore, a guide slot 154 is longitudinally formed in a side surface of the first cylinder 151. A guide pin 180 which is fastened to the second cylinder 160 is moved along the guide slot 154. A first locking depression 155 and a second locking depression 156 are respectively formed in first and second ends of the guide slot 154. The guide pin 180 is locked to the first or second locking slot 155 or 156. While the guide pin 180 moves along the guide slot 154, the second cylinder 160 moves upwards or downwards and opens or closes the frame opening.
During the fishing operation, the operation of hauling in the purse seine must be rapidly carried out, and the operation of moving the second cylinder 160 to connect the snap ring 100 to the purse line must also be rapidly conducted. For this, a spring 172 is provided in the first cylinder 151 so that the second cylinder 160 can be automatically moved upwards or downwards. The guide pin 180 can be easily moved into and locked to the first locking depression 155 or the second locking depression 156 by contraction or extension and twisting of the spring 172. Thereby, the second cylinder 160 can be automatically moved upwards or downwards, thus facilitating the operation of opening or closing the frame 110.
However, to make the twisting of the spring 172 possible, for example, first and second coupling depressions 174a and 178a are required to fix opposite ends of the spring 172, so that the overall structure is complex. This increases the production cost. Furthermore, the twisting movement of the spring 72 deteriorates the elasticity of the spring 72, thereby increasing the replacement costs of the parts.